Incongruent transition, in

chemistry Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...

, is a mass transition between two

phases Phase or phases may refer to: Science *State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter), a region of space throughout which all physical properties are essentially uniform *Phase space, a mathematica ...

which involves a change in

chemical composition A chemical composition specifies the identity, arrangement, and ratio of the chemical elements making up a compound by way of chemical and atomic bonds. Chemical formulas can be used to describe the relative amounts of elements present in a com ...

. This is contrasted with congruent transition, for which the composition remains the same. The transition may be that of

melting Melting, or fusion, is a physical process that results in the phase transition of a substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the application of heat or pressure, which inc ...

vaporization Vaporization (or vapo(u)risation) of an element or compound is a phase transition from the liquid phase to vapor. There are two types of vaporization: evaporation and boiling. Evaporation is a surface phenomenon, whereas boiling is a bulk phenome ...

or allotropism. The concept is also often extended to related phenomena, for example, incongruent dissolution of a solid by a liquid solvent, which is often encountered in

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

. The term "phase decomposition" is sometimes used to describe incongruent transition. However, it has to be kept in mind that incongruent transition is described by an

equilibrium Equilibrium may refer to: Film and television * ''Equilibrium'' (film), a 2002 science fiction film * '' The Story of Three Loves'', also known as ''Equilibrium'', a 1953 romantic anthology film * "Equilibrium" (''seaQuest 2032'') * ''Equilibr ...

. For an example, see

incongruent melting Incongruent melting occurs when a solid substance being partially melted does not melt uniformly, so that the chemical composition of neither the resulting liquid nor the resulting solid is the same as that of the original solid. For example, mel ...

References

* {{refend Physical chemistry